1. Field of the Invention
The invention relates to a piece with integrated-heat insulating covering.
2. Description of the Prior Art
Heat insulating coverings are used whenever it is necessary to comply with thermal environmental conditions inside and/outside a piece of equipment. These conditions may be related to the security of the users of said equipment, or to a requirement not to lose the heat energy accumulated in said equipment.
Thus, the exhaust pipes for gases coming from the combustion in aeroplane, boat engines or other engines, are heat insulated in concern for safety with respect to the outside and so as to maintain the temperature of the gases as far as the outlet so as not to reduce the efficiency. The same goes for certain liquid transporting ducts.
But a heat insulating covering is a device which is a complement of the equipment to be protected and, in its design, certain conditions must be complied with. It must more especially not take up too much space, be light, be easily maintained, and be impervious to the different products which, if they infiltrated inside, would adversely effect its efficiency.
In the aeronautical field in particular, the heat protection of exhaust pipes requires the accumulation of these conditions.
A heat insulating process (French Pat. No. 1 124 717) consists in using heat protection shells so as to be able to fit exactly the shape of the duct or of the wall to be insulated. These shells comprise a heat insulating padding, generally made from mineral wool, sealingly enclosed between two thin and light metal sheets made from an inoxidizable material. Heat insulating padding may be formed of several layers and, in this case, the layers are separated by reflecting screens often made from aluminum. The shape of the shells is maintained by stiffeners placed inside between the two metal sheets. The so called inner metal sheet is the one which is positioned close to the wall or the duct. The other metal sheet is said to be outside.
Such a process has drawbacks. First of all, it is difficult to provide heat insulation by means of a single shell. Two shells, complementary to each other, must in fact be used. It is then necessary to provide securing systems between the shells, so as to ensure positioning thereof on the wall.
The junction between the shells further causes a lack of thermal continuity. It frequently happens also that products harmful to the efficiency get in between the shells and the wall.
Furthermore, the wall or ducts to be heat insulated must be able to withstand different stresses and have its own rigidity, independent of that of the heat insulating covering.